Overexpression of an epitope-tagged serotonin transporter in serotonin neurons of the dorsal raphe nucleus using a defective HSV-1 vector.

The serotonin transporter (5HTT) plays a central role in serotonin neurotransmission. Abnormalities of 5HTT function have been implicated in depression, anxiety and alcohol intake. To better understand the functional role of this important molecule, we have utilized a viral vector approach to overexpress the 5HTT in regions of the rat brain. We have constructed a bicistronic defective herpes virus (HSV-1) vector that expresses both an epitope-tagged 5HTT as well as beta-galactosidase (beta-GAL) as a marker for infected cells. The vector was capable of conferring serotonin uptake activity to Vero cells in culture, indicating transfer of a functional 5HTT. Injection of the 5HTT virus into the rat brain resulted in a dense focus of specific 125I RTI-55 binding at the injection site, indicating that the virally expressed 5HTT can also bind ligand when expressed in the brain. We were also able to overexpress an epitope tagged 5HTT in serotonergic neurons in the dorsal raphe nucleus (DRN) using this approach. These data demonstrate that the levels of the 5HTT in 5HT neurons can be manipulated in the adult rodent brain using an HSV-1 vector.